Type E cavity tray installation

[davphi338]

Hi,

I've just had some cavity trays fitted due to an extension on the rear of my property. The third course up from the top of the tiles was removed and the cavity trays installed. The lead flashing was then installed one course up from the top of the tiles. This now means that I can see the black of the cavity tray protruding under the brick and they have also not put anything in the vertical mortar joint, its just a hole. I asked if there was any form of vent being put into that hole and was told no its a weep hole.

I've had a quick look at the installation procedure for these trays and it seems to me that the lead flashing should go on first and then the cavity tray sits on that and a vent goes into vertical mortar joint to act as a weep hole. Would there be any reason why the builder could not put the cavity tray in the second course up. The builder didn't want to install the trays and said they would look *rap but BC insisted on them.

 

[freddiemercurystwin]

The lead upstand should be a minimum of 150mm up from the tiles so this would normally be at least 2 bricks up from the back of the tiles, the lead should sit directly beneath the cavity tray, there should be a proprietry weep hole in the gaps to stop the bees if nothing else. If its all done correctly there's no reason it will look anything other than neat, though the edge of the tray may be poking out a bit, but with lead directly beneath it I doubt you'd notice. Unfortunately you've got a course of bricks between the tray and the lead. Its odd he's not done it lower, probably saved himself a few quid on the lead. Ask him why. Expect it'll be fine as it is but it is a bit of a bodge. Can you post a pic?

 

[davphi338]

Untitled

• davphi338
• 16 May 2009
• 1

Untitled

• davphi338
• 16 May 2009
• 1

Thanks for the reply, you say the lead flashing upstand has to be a minimum of 150mm from the tiles. My lead flashing is only covering 1 brink so its not 150mm. Could it be that the window sits lower than 150mm so they have put the flashing below the lowest window.

 

[freddiemercurystwin]

Ah well you're a bit buggered under that window. You could ask him to trim the excess off the dpc if it bothers you, its still a bit odd that he didn't do it 2 bricks high or fit the dpc 1 course lower though. The way he's done it has left the wall potentially slightly vulnerable. Thats not say it will ever leak, it probably won't just seems odd to have gone through all that effort and not to have done it quite right. He ought to stick some weepholes in there at least. Normally they'd be built in as you go. Technically he's done it wrong so you're within your rights that he puts it right, depends how much hassle you want, how amiable he is, whether you're worried or not. I'd be interested to know what building control think about it especially as they (rightly in my opinion) insisted on it. At least if BC don't like it that'll give you some more leverage with the builder if you want him to change it.

 

[davphi338]

Building control insisted on the cavity trays when the builder didn't want to install them, but when he came to visit on Thursday he didn't even look at or mention the cavity trays and said he won't be coming again until the final inspection. The builder is a good bloke and he even went to the effort of cutting the cavity tray lips so they didn't stick out so much but they spoil the look of the brickwork. He says the weep holes are actually the gaps where they haven't put any mortar on the vertical joints. He said if I wanted he would fill them all in but I think that defeats the ojtect of the cavity trays, although i suppose the water will eventually leak out of the mortar if its got in that way in the first place.

 

[freddiemercurystwin]

The theory is that any water that leaks through the outer skin of brickwork will drain down the inner face or the outer skin, hit the dpc you've just had installed and then weep out through the weep holes. Normally they'd build in things like this http://www.cavitytrays.co.uk/damp-proofing/view/1/41/1/euroweep-vent or this http://www.cavitytrays.co.uk/damp-proofing/view/1/38/1/beak-weep is a bit more subtle, they. If any water was to penetrate through that brick outer skin and the dpc were not installed it would end up inside your, thats why dpc's ought to be installed above openings or roof's.

 

[^woody^]

The installation is OK, IMO

If anything, the quality of the pointing could be better, but that's it

Plastic weep holes are just a sharp bit of marketing, and serve little purpose. Bare joints are fine

 

[noseall]

The installation is OK, IMO

If anything, the quality of the pointing could be better, but that's it

Plastic weep holes are just a sharp bit of marketing, and serve little purpose. Bare joints are fine

Believe it or not, some birds can nest in holes not much bigger than a gents wedding ring.

Some insects will see a raked perp as a housing estate.

 

[freddiemercurystwin]

Plastic weep holes are just a sharp bit of marketing, and serve little purpose. Bare joints are fine

Although rare, there are several threads on here with Posters complaining they've got bees nests etc in their cavities! And whats the advice? Fit weephole doordars, they cost hardly anything! IMO they usually look messy when installed because the bricky doesn't take much care when fitting and as mentioned you can get quite subtle ones.

 

[^woody^]

Insects will always nest somewhere.

If I quickly scan my braincells, I can recall lots of properties with weep holes, holes in mortar joints, large cracks, gaps around frames etc .... but I don't recall any mass nesting issues with any of these.

Masonry wasps/bees will make their own holes, but otherwise, the place of choice is eaves, soffits and roofs generally.

So I am very sceptical on the need for these plastic inserts. And lets not go anywhere near the need for weepholes in the first place.

 

[davphi338]

Don't think the weep holes are going to be an issue because the builder is going to fill them with mortar. There is only about 4m2 of exposed brickwork anyway.

 

[noseall]

And lets not go anywhere near the need for weepholes in the first place.

Now you are talking sense.

 

[joe-90]

That's odd noseall - when we had the big argument about them you were all in favour of them.

 

[noseall]

That's odd noseall - when we had the big argument about them you were all in favour of them.

On the contrary, if you look back at any of my comments on c.t's you will read that i have on only one occasion, in 27 years, seen evidence that a cavity tray would have been of use and that i don't see the need to retro fit them unless you reside at a coastal dwelling that can be subject to driven rain.

Our argument Joe was the idea behind the need for them.

You said it was because rain can enter a cavity at the top via an overflowing gutter or some such thing.

The rest of us said it was to do with wind driven rain against the masonry.

So, the answer is, i'm not a fan of retro fitting them and never have been.

Care to show evidence to the contrary Joey?

 

[joe-90]

The only time they ever weep is when the gutter spills backward over the wallplate and down the cavity.